“Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.” In this passage, Jesus tells a scribe that if we are to aim at one thing in life, we ought to aim at loving God with everything we are. This makes perfect sense when we consider that Christ redeemed every part of our being. Since God redeemed all we are, we are to give all we have to all of him. Nothing less is an appropriate response to salvation.
One part of loving God with all of your mind is studying theology. The word theology comes from two Greek words and literally means a word about God. When we study theology, we’re studying how God affects our views on countless issues: We study who God is, who we are, and how the world will end, to name just a few issues.
Now, anyone who has studied theology knows one thing: Theology is hard. However, if you go to church, you’d probably be surprised at how much theology you already know. After all, sermons almost always touch on some area of theology. One of the best ways to get a grasp on theology is to understand how theology is organized. Grasping this content creates a mental filing cabinet that will help you understand all of theology.
Christian systematic theology is an attempt to organize all Christian beliefs in a systematic way. To do this, theologians typically organize Christian theology into approximately eight different doctrines. As a general rule of thumb, theologians typically push the more important doctrines closer to the beginning, while relegating the less essential doctrines to the end; of course, there’s some debate as to which doctrines should be earlier and which should be later. There are also numerous subheadings beneath each one of the broad doctrines.
- The Doctrine of God
Also known as Theology Proper, the Doctrine of God contains all the beliefs that Christians hold about God. First, we believe God exists; consequently, in Theology Proper, we explain why we believe this—and the answer cannot be that the Bible says so. Instead, we typically provide some form of apology for God’s existence.
The Doctrine of God also explores a recondite, yet essential, doctrine: the Trinity. Christians throughout the Church’s two millennia-long existence have believed that God exists as a Trinity; within Theology Proper, we explain what this core doctrine means. How, for example, does God the Father relate to the Son and to the Spirit?
Another discussion topic is what God is like. God has numerous attributes: God is omniscient, omnipresent, omnipotent, immutable, unimaginably powerful, eternal, and a lot of other things that will make your head hurt if you think about them for too long! However, sometimes God’s attributes can be difficult to understand. Within the Doctrine of God, we attempt to understand God’s attributes and how the attributes relate to one another.
- The Doctrine of the Revelation
No, this doctrine doesn’t have much to do with the biblical book of Revelation; instead, this doctrine deals with how God reveals himself to us. The most common sub-heading within this doctrine is Bibliology, the doctrine of the Bible. Christians believe that the Bible is the inspired word of God to humanity; thus, within this doctrine, we discuss not only what it means for God to inspire the Bible, but also how inspiration took place. Given that the Bible is God’s inspired word, it follows that the Bible is God’s communication to us and thus bears God’s authority. Furthermore, since God doesn’t lie, many Christians affirm the Bible’s inerrancy. Inerrancy, however, can be a bit controversial because some biblical passages appear to conflict; how, for example, do the two accounts of Judas Iscariot’s death, found in Matthew 27.3-10 and Acts 1.18-19, relate to one another? Discussions of how God reveals himself through nature and our consciences and how Jesus reveals the Father to us also belong under the Doctrine of Revelation.
- The Doctrine of Humanity
Also known as Theological Anthropology, the Doctrine of Humanity attempts to understand who we are as humans within a Christian worldview. For example, the Bible states that we are all, regardless of nation, creed, or color, created in the image of God, the imago Dei; however, the Bible is less than clear on the specifics of this important designation. Within the Doctrine of Humanity, we attempt to understand what it means to be made in God’s image. Though we were made in God’s image, we know that we’ve messed something up through our sin. Thus, the Doctrine of Humanity also explains how we are still in God’s image after the Fall; furthermore, Theological Anthropology discusses the nature of and penalty for sin. Of contemporary importance, the doctrine of humanity also discusses the proper relationship between males and females, homosexuality, and all the other en vogue sexual idiosyncrasies running rampant through western society.
- The Doctrine of Christ
The Doctrine of Christ, or Christology, provides answers to the problems raised by the Doctrine of Humanity. Whereas the Doctrine of Humanity explains that we are all sinners, the Doctrine of Christ explains how Christ redeems us from our sins.
Not only does Christology explain Christ’s salvific work, Christology explains who Jesus was. All true Christians believe that Jesus was 100% God and 100% human; this, however, is difficult to understand. If Jesus is God, then he seems to be omnipresent; if Jesus is a man, then he seems not to be omnipresent. Further, God knows everything, so was Jesus lying when he claimed that he didn’t know something in Matthew 24.36? Christology, which I personally find to be the most difficult of all eight doctrines, seeks to explain how Jesus can really be fully God and fully human.
- The Doctrine of the Holy Spirit
While the Doctrine of Christ explains how Christ purchased our redemption, the Doctrine of the Holy Spirit explains the Holy Spirit’s role in applying redemption to the lives of believers. Whereas Christ opened the door for salvation, the Holy Spirit calls unregenerate human beings to salvation. Once saved, the Holy Spirit seals the believer until the day of redemption. The Holy Spirit then leads the new believer in a new lifestyle in which the believer is slowly transformed into the image of Christ. This takes place through spiritual gifts, conviction over sin, special direction from the Holy Spirit to the believer, developing godly habits, destroying sinful habits, etc. Overall, the Holy Spirit is the member of the Trinity that is present in and works within the lives of individual believers.
- The Doctrine of Salvation
Next is the Doctrine of Salvation, or Soteriology. During the different periods of church history, different doctrines have been hotly debated at different times. The Doctrine of Salvation is the hot doctrine of the current period of church history because of the Calvinism/Arminianism debate.
We know from previous doctrines that we are all sinners, that God saves those who believe through Christ’s sacrificial death, and that the Holy Spirit applies the work of Christ to the lives of believers. The Doctrine of Salvation asks how and in what order all of this takes place. Though this may seem simple initially, there are numerous issues under the surface: If God wants all people to be saved (2 Peter 3.9), then how come some people don’t get saved? Since God knows everything, He knew that Jones (a made-up man) would not accept salvation in Christ; so, did Christ die for Jones too? If so, it seems like Christ wasted something; however, on the other side, if Christ didn’t die for Jones, then it’s hard to see how God genuinely wanted Jones to get saved in the first place.
Another key feature of Soteriology—and also an essential part of the Calvinism/Arminianism debate—is the order of salvation, the ordo salutis. The general idea is that salvation is a broad term that has multiple stages such as adoption, justification, regeneration, sanctification, and glorification. These all refer to various events in the Christian life: When we place our faith in Christ following the Holy Spirit’s call to salvation, God justifies us on the basis of faith alone. At the same time, God adopts us into his family while also regenerating us. However, we still act like a bunch of heathens; so, we begin the lifelong process of sanctification in which the Holy Spirit remakes us in Jesus’s image. When we die, we go to heaven where sanctification is instantly completed in glorification, which means that we are now perfect.
- The Doctrine of the Church
Ecclesiology, or the Doctrine of the Church, is all about what the church is, what the church does, and why the church exists. There are two churches: the local church and the universal Church (the capital C is important). The local church is the way that we see, understand, and experience the church on this side of eternity. Within the local church, there are different roles: The pastor has a role, the deacons have roles, and the members have roles. Ecclesiology explains who should be in these roles and what they should do.
Local churches (at least if they’re non-sacramental) also practice the two ordinances: baptism and communion (AKA Lord’s Supper or the Eucharist). In Ecclesiology, we discuss who should participate in the ordinances and what the ordinances mean. If a local church is a sacramental church, they’d have a list of the sacraments that they’d list at this point while discussing what the sacraments are and what the sacraments mean.
The universal Church is the way that God sees the Church. God knows which members of the local church are real Jesus followers and which are phony. The universal Church is the real Church composed of all true believers from all places spread throughout all times. If you’re following Jesus, then you’re a member of the universal Church whether or not you’re a member of a local church. If you aren’t following Jesus, then you can be a member of as many local churches as you want, but you aren’t a member of the universal Church.
- The Doctrine of Last Things
Finally, the Doctrine of Last Things, also known as Eschatology, answers questions about how the world will end, judgment day, and what heaven and hell are like. How the world will end is a hot topic for popular level theologies and lay theologians; this doctrine, however, is much more ambiguous and much less essential than the previous seven doctrines. Though there are a variety of systems in Ecclesiology, what everyone agrees on and what the Bible teaches is that Jesus is coming back.
Here are the three main systems: amillennialism, post-millennialism, and pre-millennialism. One of the main differences between each system is the understanding of how Revelation 20.1-3’s reference to the 1000-year period relates to Christ’s return. Amillennialists believe that Jesus is simply going to come back one day. According to amillennialists, the 1000 years in Revelation 20 doesn’t really mean 1000 literal years, this number is merely figurative. Post-millennialists, who are virtually non-existent in the modern day, believe that we will usher in the millennium by spreading the gospel; after we’ve spread the gospel and the world has accepted Christ as savior, Christ will return. Pre-millennialists come in many different flavors. The basic idea for a pre-millennialist is that Christ will return to earth and institute the millennium; some believe in a rapture and seven years of tribulation, though you can be a pre-millennialist without the rapture and tribulation.
Theology can be a hard subject! I haven’t even touched on many of the issues within theology. However, if you can grasp this content, then you’ll be well on your way to gaining a better understanding of theology.
Notes & Sources
 Mark 12.31, NIV.
 The Holy Spirit’s identity is usually explained in the doctrine of God’s discussion of the Trinity.